I'm guessing it's alluding to the fact that Rock and subsequently Metal were inspired in earlier times by Blues and Soul.
And the top guy, it's just the usual far-lefty blue checkmark accusing every white person of cultural appropriation.

There's also the fact that rock 'n' roll was a genre of black origin; its later co-opting by white artists was actually encouraged by black artists for the sake of furthering improvements in race relations.

The scrutiny of rock nowadays is mainly a byproduct of how lily-white the genre became from the Beatles onward, due to a combination of lack of promotion for black rock artists (outside of Hendrix) and black musicians shifting focus to R&B and soul with the rise of Motown (with R&B in turn paving the way for funk, which paved the way for disco, which paved the way for hip-hop).

The general consensus I've come up with is that claiming that there are no good white rock stars is reckless and ignorant and taking inspiration from black artists is not inherently bad if it's done earnestly and respectfully (e.g. Talking Heads and Peter Gabriel's respectful approaches vs. Iggy Azalea's shallowness), but at the same time the wider music industry ought to be more open to more black and otherwise nonwhite rockers in addition to white ones. Almost all of the first inductees in the Rock and Roll Hall of Fame were the original black rockers, yes, but new talent also deserves a spotlight.